Process Modeling
1
Modeling System Behavior
2
State Transition Diagrams
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A state transition diagram is a model that depicts a
system’s states and the events that cause the system
to change states.
A state is any observable mode of behavior for the
system.
The state transition diagram also shows what actions
are taken as a consequence of an event
Such models are often called finite state machine
models
3
State Transition Diagrams – An Example
Following is a state transition diagram for software controlling
a printer. In this simplified model, we’ve identified five
distinct states: idle, ready, printing, jammed, out_of_paper.
The arrows represent transitions from one state to another.
Along each arrow we note the event triggering the state
change (above the horizontal rule) and the action taken in
response to the event (below the horizontal rule).
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State Transition Example (cont’d)
trigger
action
print request
ready new job
idle
job complete
stop printing
new job
initiate print
ready
resume job
initiate print
printing
jammed
display jam msg
paper loaded
ready resume job
no paper
display paper msg
out_of_paper
jam corrected
ready resume job
jammed
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Activity
Consider the software that controls the functions of a cruise
control device on an automobile. Work with your team to create a
state transition diagram for this system.
The particular device we’re working has the usual cruise control
functions, plus the following enhanced ones: 1) if your vehicle pulls
within 50 feet of a vehicle in front of you, an active cruise control
device will turn itself off if it is set for more than 45 mph; 2) when
you tap the brake once, the cruise control speed is suspended, but
may be reinstated by pressing the resume button; 3) if you tap the
brake more than once or if you hold the brake down for more than 2
seconds, the cruise control device will turn itself off in which case
the speed setting is cancelled and will have to be reset when you
re-engage the device.
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Dialog Maps
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User interfaces can often be regarded as a
finite state machine model
Thus, state transition diagrams can be used to
model these
Such state transition diagrams are referred to
as dialog maps (also sometimes called site
maps when used with Web development)
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Dialog Maps as Finite State Machines
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Each dialog element (menu, screen, dialog
box, etc.) can be viewed as a state
The user can then navigate to another dialog
element (i.e. change states)
The possible elements and the navigation
paths between them can be modeled as a state
transition diagram
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Dialog Maps – An Example
1 start
transaction
terminated
request to
access
cancel registration denied
Error
Message Displayed
cancellation
data
invalid
try again
Registration
Information
Accessed
cancellation
request
cancellation
confirmed
cancellation
not allowed
Cancellation
Performed
Cancellation
Denied
update submitted
update not
allowed
Route
Request
Modeling User Interaction to Cancel a Seminar
Registration in the Seminar Registration System we
worked on earlier.
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Dialog Maps – An Example
1 start
transaction
terminated
request to
access
cancel registration denied
Error
Message Displayed
cancellation
data
invalid
try again
Registration
Information
Accessed
cancellation
request
cancellation
confirmed
cancellation
not allowed
Cancellation
Performed
Cancellation
Denied
update submitted
update not
allowed
Route
Request
Possible Application for a Decision Tree/Table
Modeling User Interaction to Cancel a Seminar
Registration in the Seminar Registration System we
worked on earlier.
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Activity
Consider the Seminar Management System we’ve been working on.
Work with your team to create a dialog map that models the
seminar administrator’s interactions with the system in obtaining an
instructor for a seminar.
Refer to the Level 0 DFD for this system on the next slide to refresh
your memory about it if needed.
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Print
Vendor
eval_request
Email Sys
Attendee
seminar_notification
request_for_eval
Selected
Venue
instructor_reserved
no_instructor_available
booking_denied
instructor_request
venue_request
venue_reserved
venue_options
Seminar
Administrator
venue_choice
no_venue_avail
Proposed
Seminar
Management
System
SMS
venue_pmt_info
instructor_pmt_info
final_roster
Instructor Info
venues_available
Accounts
Payable
Seminar
Registration
System
inst_dates
dates_avail
email_address
Venues Info*
roster_sign-in
Instructor
final_roster
Attendee Info*
* Transfer/Maintenance TBD
Dialog Maps as Abstraction of User Interface
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Dialog maps can be viewed as high-level
abstractions of user interfaces
Show the dialog elements and navigational
links among them
They do not reveal, or even take into account,
detailed screen designs or data field definitions
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Dialog Maps and Prototypes
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A dialog map makes a good preliminary model
to use before beginning the construction of a
prototype
Provides vehicle for a high-level discussion
with users about the interface functionality -without getting bogged down in screen
appearance and data definition details
Excellent model for discovering missing
requirements and misunderstood requirements
relative to user interactions
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Modeling Processes and Functionality
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Specifying Function
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Define how data changes as it flows through the
system
Identify the transformations (or functions) that must be
performed on data to implement these changes
Specify performance targets where appropriate
The use of Data Flow Diagrams (DFDs) is one of the
most popular functional modeling techniques
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Data Flow Diagrams (DFDs)
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The emphasis in data flow modeling is on
modeling function (i.e. the process that enables
the flow of data)
We’ve seen some examples of this technique
already in our use of Level 0 DFDs
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Example Level 0 Data Flow Diagram
Employee
employee_data
payroll_parameters
Hourly
Employees
hours_worked
Proposed
Hourly Payroll
System
weekly_
payroll_
summary
Corporate
Payroll
System
weekly_check
weekly_payroll_report
Plant Manager
payrate_parameters
Employee
employee_data
Hourly
Employees
ded_parameters
2
Compute
Gross
Pay
hours_worked
gross_pay
hrs_emp-data
3
1
Match
Hours &
Emp_Data
4
deductions
7
Create
Reports
Prepare
Check
Data
5
Print
Check
weekly_payroll_summary
Compute
Deductions
ded_data
weekly_check
Corporate
Payroll
System
payroll_data
weekly_payroll_report
6
check_data
Tabulate
Summaries
Plant Manager
Payroll System Level 1 Data Flow Diagram
Abstraction and Refinement
with DFDs
Abstraction
proble
m
Refinement
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Activity
Recall the Level 0 DFD for our Seminar Management System from the
previous class (given on the next slide). Let’s consider the steps we
might take to refine this into a Level 1 DFD.
1)
2)
3)
4)
With your team, identify the major processes you might like to
have in the Level 1 DFD – use the Payroll Example for a guide
if needed.
Once we reach a consensus on these, we will break the work
up.
Each team should choose two of these processes and develop
all the inputs and outputs they would have. Keep in mind that
you may show some internal flows that didn’t appear on the
Level 0 DFD, and you may also show more detail in the data
flows at this level than you had on the Level 0 DFD.
All data flows used should be consistent with those we used in
the Level 0 DFD
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Print
Vendor
eval_request
Email Sys
Attendee
seminar_notification
request_for_eval
Selected
Venue
instructor_reserved
no_instructor_available
booking_denied
instructor_request
venue_request
venue_reserved
venue_options
Seminar
Administrator
venue_choice
no_venue_avail
Proposed
Seminar
Management
System
SMS
venue_pmt_info
instructor_pmt_info
final_roster
Instructor Info
venues_available
Accounts
Payable
Seminar
Registration
System
inst_dates
dates_avail
email_address
Venues Info*
roster_sign-in
Instructor
final_roster
Attendee Info*
* Transfer/Maintenance TBD
Workflow Diagrams
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A workflow diagram shows a high-level view of a
business process, indicating steps, inputs, and
outputs
These do not typically attempt to show any decisions
The swimlane variant of the workflow diagram shows
participants (people or systems) responsible for
carrying our various steps
Each participant has its own swimlane
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Workflow Diagrams
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Useful for analyzing existing business processes
Can show impact on existing processes of requested
changes
Can identify opportunities for process improvement
Can model process changes or new processes
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Workflow Diagram Example (with swim lanes)
Process Name: Complete an Online Customer Order
swim lanes
Input: Customer profile information, including
billing and shipping information
Customer
start
sign in
submit
order
Order
Approval
confirm
available
Inventory
check
inventory
Order
Fulfillment
Shipping
confirm
payment
adjust
inventory
assemble
order
pack
order
ship
order
stop
Output: Shipping bill and
tracking information
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Activity
Consider the Seminar Management System we’ve been working on.
Work with your team to create a workflow diagram (with swim lanes)
for the process of scheduling a seminar venue. Note that this
process should include the preliminary process/activity of obtaining
an instructor.
Refer to the earlier Level 0 DFD for this system to refresh your
memory about it if needed.
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Writing Requirements
With your team, utilize the Level 0 DFD and the workflow diagram
the team created to write a draft of the business requirements for
the Seminar Management System.
Organize the requirements in categories to make them easier to
read and change as necessary.
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Review of Key Learning Outcomes
When you complete this course you will be able to:
1)
Describe why models are useful in discovering business requirements
2)
Explain how the two concepts of abstraction and refinement work within
modeling to help manage complexity
3)
Identify the three major views of systems used in modeling
4)
Give examples of some types of models that are common for these views
5)
Explain and use state transition diagrams to model system behavior
6)
Explain and use dialog maps to model user interaction with a proposed
system
7)
Relate dialog maps and prototyping
8)
Explain and use Level 0 and Level 1 Data Flow Diagrams to model system
functionality
9)
Explain and use workflow diagrams to model business processes
10)
Explain and use swimlanes with workflow diagrams
11)
Show how models can be used to help create and validate business
requirements
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